Transgender people are a diverse group of individuals whose gender identity differs from their sex assigned at birth. They express their gender-variant identity in various ways and through a multitude of self- labels, both within and outside of binary conceptualizations of sex/gender as either male or female, man or woman, masculine or feminine. While public awareness of this diversity has grown, our understanding of transgender people's experience is limited by a lack of systematic research on their identity development. Health inequities documented among the U.S. transgender population include depression (44%), suicidal ideation (54%) and attempts (31%), anxiety (33%), smoking (36%), and HIV infection (12% based on self- report; 28% on testing). Social stigma attached to gender nonconformity has been proposed as a major contributing factor to these health inequities. Previous research found that the vast majority of transgender individuals experienced discrimination. Much of the data, however, is limited by the use of small convenience samples of transgender women with a history of sex work, recruited from AIDS and social service agencies. The goal of this study is to move beyond these limitations by using purposive, venue-based sampling to recruit a broad, diverse sample of transgender people in 3 U.S. cities--New York, San Francisco, and Atlanta-and enroll them into a mixed-method longitudinal study to test an adaptation of the minority stress model, investigating vulnerability, risk and resilience in the context of identity development. The aims of the study are: (1) To describe the process of transgender identity development based on qualitative lifeline interviews with a sample of 90 transgender individuals ages 16 and older, and identify periods of acute vulnerability and characteristics of resilience; (2) Informed by findings from Aim 1, to refine a model combining identity development, minority stress, and resilience, and to develop/adapt measures to assess the model's key constructs; (3) To test the model of resilience in a cohort of transgender individuals (N = 480) stratified by city, gender, and age, and follow them over time (baseline, 1-, 2-, and 3-year follow up interviews); and (4) To triangulate qualitative and quantitative data on identity development and minority stress processes in order to inform the future development and testing of intervention strategies aimed at fostering resilience and reducing stigma and discrimination. By achieving these aims, this study will make a significant advance in scientific knowledge about gender identity development, minority stress processes (enacted stigma, felts stigma, concealment, shame and their impact on health and psychosocial adjustment), minority coping (on an individual as well as community level), and the development of resilience over time. The study is innovative in its focus on an understudied minority population, the application of the lifeline interview method to this population, and the adaptation and testing of the minority stress model within the context of transgender identity development.